The amount of radioactive cesium is five times more than the limit set by a local fisheries cooperative of 50 becquerels per kg. It is also sharply higher than Japan's national standard in general foods of 100 becquerels per kg.

In response, Japan's national nuclear emergency response headquarters on Monday ordered a ban on the shipment of the fish caught off the waters of Fukushima.

Early in February, radioactive cesium 10 times above permitted levels in Japan were detected in the same area.